The helix is a cylindrical coil conductor, such as employed in high-frequency electronics in, among other things, resonator and antenna structures, in particular in portable radio appliances, such as mobile telephones.
Antennae in which use is made of a helical antenna supported on a support plate inside the helix have been proposed in GB Patent Application No 2 280 789. The publication in question contains a proposal for a structure where strip areas which consist of a conducting material and which constitute a helix antenna are formed on the surface of a dielectric substrate. The conducting areas are, for example, created on one side only of the substrate, which substrate is bent into the form of a cylinder, thus producing a helical antenna. Another method is to produce, on both sides of the substrate, conductor strips which are joined to conductor strips on the opposite side, so that a helical antenna element is obtained. The publication also contains a proposal for the connection of a whip antenna to a helix antenna with a separate connecting means through which the whip component may move. U.S. Pat. No. 4,935,747 proposes a helix antenna where the helix is placed around a support member which in cross section has the shape of a cross. The helix and support member are against a reflector on which a strip line is formed for antenna feed.
In both of the cases described above, the support member inside the helix is intended to retain and support the helical form, only the helical component being a radiator. The problem with such a solution is that other possible components of the antenna, such as the transmission line or the whip antenna, have to be connected to the helix by other means and have to be attached to the support structure of the antenna by other means.
An antenna formed from conductor patterns on the surface of a dielectric substrate has been described in U.S. Pat. No. 5,021,799. This patent proposes a dipole antenna, which is formed with the aid of conductor strips which are created on the surface of the substrate. The antenna in the patent in question has no helical component whatsoever. The problem with this type of solution lies in its large size. By using a helix it is possible to restrict the physical dimensions of an antenna designed for a particular wavelength range.
The combination of a dielectric plate and a helix is also employed in the helix-comb filter produced by LK Products Oy, which is described in Finnish Patent No. 78198. The patent also proposes a resonator structure, in which there is a cylindrical coil conductor forming the helix-resonator, which conductor is supported on a plate situated inside it and made from an insulating material. On the insulation plate, strip lines are used to form an electrical circuit to which the helix resonator is connected. This patent does not, however, concern use of the structure as an antenna, since in the design of resonator structures it is desirable to eliminate radiation to the environment.
EP application No. 590 534 describes the use of a helix in combination with a dipole antenna pattern formed on a dielectric plate. The application describes an antenna which can be retracted into a housing, whereby conductive patterns on the dielectric plate form both a sliding contact and an antenna pattern. The application does not, however, present a structure which could easily be used in mass production for producing many different types of antennas.